Variation in guns laws from state to state may be complicating law enforcement efforts, especially in regions such as New England, where states are split between restrictive and largely hands-off approaches to gun ownership, according to some gun law specialists and gun control advocates.

Authorities in Massachusetts, which has some of the toughest gun laws in the nation, recovered 1,737 firearms used in crimes during 2011. Of the 1,020 firearms that the Bureau of Alcohol, Tobacco and Firearms traced to their state of origin, just 351
originated in Massachusetts.

About 250 of the 1,020 guns traced came from nearby states with
less restrictive gun laws, including 133 from New Hampshire and 79 from Maine.

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The large percentage of guns used in crimes that originated in other states carries troubling implications, said Jake Wark, a spokesman for Suffolk District Attorney Daniel F. Conley.

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“Clearly that has an effect on gun violence in Massachusetts, and especially in Boston,” he said.

The gun-tracing statistics back up calls for national gun-control laws, said Brian Malte, director of legislation for the Brady Campaign to Prevent Gun Violence. “Massachusetts gun laws are being undermined by surrounding states with weak gun laws,” he said.

Questions about the state-by-state differences in gun laws are getting new attention
following the recent
attack in a Colorado theater, where a
heavily armed man fatally shot 12 people at the midnight opening of “The Dark Knight Rises.”

According to the Law Center to Prevent Gun Violence, which each year ranks states based on the strength of their gun laws, Massachusetts, Connecticut, and Rhode Island all rank in the top 10 — third, fourth, and ninth respectively. Vermont and Maine have what are considered some of the
least restrictive gun laws in the nation — 46th and 38th. New Hampshire is in the middle of the pack, ranking 24th.

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The rankings are based on state laws addressing a host of gun-related categories, including assault weapons, conceal-and-carry permits, gun and ammunition sales, and high-volume magazines, said Lindsay Nichols, staff attorney for the law center, which supports tougher gun laws.

The trend among states is toward fewer regulations on gun ownership, Nichols said.

“Nationally, there is a movement to weaken gun laws,” Nichols said. “The national gun lobby has put a lot of effort at chipping away at state gun laws, and it’s affecting New England.”

Rather than tackle issues such as assault weapons bans and conceal-and-carry laws, she said, gun lobbyists have worked to push a number of smaller expansions of gun rights. She cited two laws passed last year in Maine: one allowing the possession of guns in state parks and at historic sites, and the other prohibiting employers from restricting workers from storing guns in their vehicles in company parking lots.

But gun-rights advocates in New England say the recent legislation in Maine is a step in the right direction. If Massachusetts were to adopt gun laws similar to those in neighboring states, they argue, the state would see a dip in crime.

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“We don’t have any firearms problems up here,” said Ed Cutler, legislative director of the Gun Owners of Vermont, who said the number of guns leaving states with fewer gun restrictions, such as Vermont, is “blown way out of proportion.”

Cutler said that in a state such as Vermont — where he estimates 75 percent of households own at least one gun — a potential mass murderer would be stopped in a public place because bystanders might be armed.

“Vermont might have some of the most lax gun control in the country. We’re also the safest state in the country,” he said. “We are the safest state due to the large number of guns in this state.”

Laws in Massachusetts and Connecticut are unreasonably restrictive, said Bennett Prescott a spokesman for the Connecticut Citizens Defense League, a group that promotes gun ownership.

He said the impulse to enact more restrictive laws following a mass murder is understandable, but he maintains that making gun ownership more difficult is not the way to prevent such violence.

“Whenever there is a tragic event like this, there is always some effort to say, ‘What can we do?’ or ‘What could we have done,’ ” he said. “But there is nothing you can do to stop a madman.”

Gun-control advocates have highlighted reports that James Holmes, the accused Colorado shooter, used an assault weapon that would have been banned under a federal law that expired in 2004.

Those looking to cut gun violence, however, should look beyond rifles, said Jack Levin, a criminology professor at Northeastern University and co-director of its Center on Violence and Conflict.

“The gun problem in this country has little to do with the prevalence of semiautomatics,” Levin said. “There are 15,000 single-victim murders in the United States every year, about two-thirds of which are committed with firearms. The overwhelming majority of these homicides are committed with handguns.”

Advocates on both sides of the gun-control debate agree that bans on assault weapons fail to
eradicate high-powered guns from a state, especially with the rise in weapon sales on the Internet and at gun shows.

“Even in states with the strongest gun laws, there are still loopholes that need to be filled,” Nichols said.

One example, she said, was that Massachusetts does not require background checks at the point of purchase. Instead, once residents are granted a firearm permit, they may buy as many guns and as much ammunition as they like without undergoing further checks until that permit expires.

Meanwhile, gun manufacturers continue to alter weapons to exploit loopholes in state gun-control legislation, said Todd McGhee, who served as a Massachusetts State Police officer before founding Protecting the Homeland Innovations, a counterterrorismtraining firm.

“Overlegislating a particular topic is not going to keep our public safer,” McGhee said. “We need to spend more time focusing on the behavior of the individual people purchasing a firearm.”

Wesley Lowery can be reached at wesley.lowery@globe.com. Follow him on Twitter @WesleyLowery. Adam Sege can be reached at adam.sege@globe.com. Follow him on Twitter @AdamSege.